I really doubt it’s deliberate. I have not seen any systematic pattern. Just the usual type of errors (mostly in the direction that fits the narrative) that one would expect from an individual who is not exercising utmost care.

I’ve certainly seen other authors systematically misquote statistics, and mean to: pretty much everything they cite is misleading in some way. It’s hihgly uncharitable to assume Ms. Gaines is a haphazard propagandist (because she doesn’t always twist her stats) than that she is a haphazard advocate who intends to be honest.

Finally, you don’t seem to have understood my statement that you say you disagree with. That biases are plentiful has nothing to do with whether you can conclude bias when you manipulate only a race-linked variable and see an effect. You can conclude bias in this case. There is no way out. You might want to analyze the whole picture to find the ultimate source of the racial bias, if it is deeper than “just race”. If you use race alone as a cue to trigger bias, then it is definitionally a racial bias, regardless of what circumstances led you to develop that bias or what other biases are around. You might want to look at the whole picture and the history before looking for a good solution, but you don’t need to do that in order to determine that there is racial bias.